U.S. patent number 4,510,418 [Application Number 06/644,905] was granted by the patent office on 1985-04-09 for rapid start fluorescent lamp with a bimetal electrode disconnect switch.
This patent grant is currently assigned to GTE Products Corporation. Invention is credited to John W. Anderson, Jr., William J. Roche.
United States Patent |
4,510,418 |
Anderson, Jr. , et
al. |
April 9, 1985 |
Rapid start fluorescent lamp with a bimetal electrode disconnect
switch
Abstract
A rapid start fluorescent lamp having a glass envelope with a
phosphor coated inner surface, a low pressure gas fill and an
electrode at each end includes at least one electrode disconnected
switch having a bimetal switch normally closed at room temperature
and open at a predetermined temperature higher than room
temperature with the bimetal switch connected to the electrode and
to an electrical lead extending from the lamp to an energization
source.
Inventors: |
Anderson, Jr.; John W.
(Ipswich, MA), Roche; William J. (Merrimac, MA) |
Assignee: |
GTE Products Corporation
(Stamford, CT)
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Family
ID: |
27051566 |
Appl.
No.: |
06/644,905 |
Filed: |
August 28, 1984 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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632262 |
Jul 18, 1984 |
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546072 |
Oct 27, 1983 |
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494841 |
May 16, 1983 |
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Current U.S.
Class: |
315/73; 315/106;
315/119; 315/74 |
Current CPC
Class: |
H01J
61/54 (20130101) |
Current International
Class: |
H01J
61/54 (20060101); H01J 007/44 (); H01J 017/34 ();
H01J 019/78 (); H01J 029/96 () |
Field of
Search: |
;315/73,74,76,106,107,119,362 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Chatmon; Saxfield
Attorney, Agent or Firm: Buffton; Thomas H.
Parent Case Text
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is a continuation-in-part of application Ser. No.
632,262, filed July 18, 1984, now abandoned which was a
continuation of application Ser. No. 546,072, filed Oct. 27, 1983,
now abandoned, which was a continuation-in-part of application Ser.
No. 494,841, filed May 16, 1983, now abandoned.
Claims
What is claimed is:
1. A 40-watt type rapid start fluorescent lamp operable at a
current in the range of about 350 to 475 ma and having an envelope
with a phosphor-coated inner wall surface, a low pressure fill gas,
an electrode within each end of the envelope and a pair of
electrically conductive leads passing through each end of said
envelope for coupling each of said electrodes to an energization
source, said fluorescent lamp characterized by the improvement
wherein an electrode disconnect switch is affixed to at least one
of said pair of electrical leads associated with at least one of
said electrodes within said envelope, said electrode disconnect
switch including a bimetal switch operable at temperatures in the
range of about 75.degree. C. to 300.degree. C. and normally closed
at room temperature and open at a predetermined temperature higher
than room temperature and spaced at least 8.0 mm from said
electrode and a pair of electrical conductors coupled to said
bimetal switch, one of said pair of electrical conductors of said
disconnect switch connected to one of said pair of electrically
conductive leads of said lamp and the other of said pair of
electrical conductors of said disconnect switch connected to said
electrode with the other of said pair of electrically conductive
leads of said lamp coupling said electrode to said energization
source.
2. The rapid start fluorescent lamp of claim 1 wherein said
electrode disconnect switch is disposed within a glass bottle.
3. The rapid start fluorescent lamp of claim 1 wherein said bimetal
switch is in the form of a substantially U-shaped bimetal
switch.
4. The rapid start fluorescent lamp of claim 1 wherein said
electrode disconnect switch is disposed within a hermetically
sealed bottle having a fill gas selected from the group consisting
of nitrogen, the noble gases and combinations thereof.
5. The rapid start fluorescent lamp of claim 1 wherein said
electrode disconnect switch has an average spacing from said
electrode of not less than about 8.0 mm and not more than about
14.0 mm.
6. The rapid start fluorescent lamp of claim 1 wherein said
electrode disconnect switch is operable at a temperature in the
range of about 140.degree. C. to 180.degree. C.
7. In a 40-watt type rapid start fluorescent lamp operable at a
current in the range of about 350 to 475 ma and having a glass
envelope with a phosphor coated inner wall surface, a fill gas and
a pair of spaced electrodes disposed within the opposite ends of
said glass envelope with a pair of electrically conductive leads
passing through each end of said envelope for coupling said
electrodes to an energization source, the improvement comprising at
least one electrode disconnect switch disposed within said lamp and
having an average spacing of at least 8.0 mm from one of said
electrodes, said electrode disconnect switch having a bimetal
switch means normally closed at room temperature and open at a
predetermined temperature higher than room temperature with a pair
of electrical conductors connected to said bimetal switch means,
one of said pair of electrical conductors coupling said bimetal
switch to said electrode and the other of said pair of electrical
conductors coupling said bimetal switch to one of said electrically
conductive leads of said lamp and said other electrically
conductive lead coupling said electrode to said energization
source.
8. The improvement of claim 7 wherein said bimetal switch means is
hermetically sealed within a glass bottle and operable at a
temperature in the range of about 75.degree. C. to 300.degree.
C.
9. The improvement of claim 7 wherein said bimetal switch means is
hermetically sealed within a glass bottle having a fill gas therein
selected from the group consisting of nitrogen, the noble gases and
combinations thereof.
10. The improvement of claim 7 wherein said bimetal switch means is
hermetically sealed within a glass bottle and operable at an
average spacing of about 8.0 to 14.0 mm from said electrode.
11. The improvement of claim 7 wherein said bimetal switch means is
hermetically sealed within a glass bottle and operable at a
temperature in the range of about 140.degree. C. to 180.degree. C.
Description
TECHNICAL FIELD
This invention relates to rapid start fluorescent lamps and more
particularly to rapid start fluorescent lamps having a bimetal
electrode disconnect switch affixed to one electrode for
discontinuing heater current flow upon effecting conductivity of
the lamp.
BACKGROUND ART
In the fluorescent lamp art both preheat type and rapid start type
fluorescent lamps are commonly encountered. In the preheat type of
fluorescent lamp, heater current flows through the electrode only
during lamp ignition whereupon an external voltage sensitive
starter opens the heater current circuit and discontinues heater
current flow. In contrast the rapid start fluorescent lamp normally
has a constant heater current flow through each electrode both
during ignition and operation of the lamp. Unfortunately, heater
current flow during operation of the rapid start fluorescent lamp
is lost power which obviously reduces the operational efficiency of
rapid start fluorescent lamps.
Numerous suggestions have been made for enhancing efficiency of
rapid start fluorescent lamps. For example, U.S. Pat. Nos.
4,052,687; 4,097,779; 4,114,968; 4,156,831 and 4,171,519, all
assigned to the Assignee of the present application, suggest
numerous configurations for enhanced operation of rapid start
fluorescent lamps. Generally, each provides a thermally responsive
circuit breaker suitable for use in discontinuing heater current
upon operation of the fluorescent lamp.
However, it has been found that problems still exist. For example,
it has been found that a problem occurs whenever the thermally
responsive circuit breaker extends in a direction parallel to the
electrode of a lamp but for a distance greater than the length of
the electrode. Thereupon, positioning the lamp envelope properly is
encumbered because the envelope tends to undesirably contact the
circuit breaker when the circuit breaker and lamp electrodes are
being inserted into the envelope. Such an encounter is obviously
undesirable, and especially so in a high production manufacturing
process.
In another aspect, it has been found that positioning of the
circuit breaker too close to the electrode has a deleterious effect
upon the life span of the fluorescent lamp. More specifically,
closely spacing the circuit breaker to an electrode generating heat
tends to significantly reduce the life span of the fluorescent lamp
wherein the electrode is located.
In still another aspect of the invention, it has been found that
the consistency and repeatability of operation of a circuit breaker
disposed within a discharge lamp can be adversely affected when
left unprotected from the environment within the discharge lamp. In
other words, a bimetal switch means placed nearby an activated
electrode within a discharge lamp may be deleteriously affected
when protection is not provided such that the bimetal switch
surfaces are not isolated from the environment surrounding the lamp
electrode.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the present invention is to provide an enhanced rapid
start fluorescent lamp. Another object of the invention is to
improve the operating efficiency of a rapid start fluorescent lamp.
Still another object of the invention is to improve the
capabilities for manufacture of the above-described enhanced rapid
start fluorescent lamp. A further object of the invention is to
reduce the energy requirements during operational use of a rapid
start fluorescent lamp.
These and other objects, advantages and capabilities are achieved
in one aspect of the invention by a rapid start fluorescent lamp
having an envelope with a phosphor-coated inner wall surface, a low
pressure fill gas, an electrode within each end of the envelope and
a pair of electrically conductive leads passing through each end of
the envelope for coupling an electrode to an energizing source
wherein an electrode disconnect switch has a bimetal switch means
normally closed at room temperature and open at a predetermined
temperature higher than room temperature and spaced from at least
one of the electrodes.
In another aspect of the invention, a rapid start fluorescent lamp
has an electrode disconnect switch therein which includes a bimetal
switch means within a glass bottle with a pair of electrical
conductors connecting the bimetal switch means to an electrode
within the lamp and to an electrical lead passing through the
discharge lamp to an energizing source.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view, partly in section, of one end of a
rapid start fluorescent lamp prior to processing;
FIG. 2 is an elevational view, partly in section, of one end of a
rapid start fluorescent lamp of the invention; and
FIG. 3 is a chart illustrating the relative life of a 40-watt type
rapid start fluorescent lamp with regard to the average or mean
distance of an electrode disconnect switch from the lamp
electrode.
BEST MODE FOR CARRYING OUT THE INVENTION
For a better understanding of the present invention, together with
other and further objects, advantages and capabilities thereof,
reference is made to the following disclosure and appended claims
in conjunction with the accompanying drawings.
Referring to FIGS. 1 and 2 of the drawings, a rapid start
fluorescent lamp suitable for processing includes an elongated
glass envelope 5 having a coating 7 of phosphor on the inner wall
surface of the envelope 5. A glass stem member 9 is sealed into the
end of the envelope 5 and includes a pair of electrical leads 11
and 13 sealed therein and passing therethrough. An end cap 15 is
telescoped over and attached to the end of the glass envelope 5 and
includes a pair of pins 17 and 19 electrically connected to a
portion of the electrical leads 11 and 13 and formed to provide
electrical connection to an external potential source of
energization (not shown). Moreover, the envelope 5 has a gas fill
therein selected from the group consisting of argon, xenon,
krypton, neon, helium and combinations thereof.
Within the envelope 5, an electrode 21 has one end thereof
connected to one of the electrical leads 13 and a longitudinal axis
which extends in a direction substantially normal to the direction
of the electrical leads 11 and 13 (i.e., normal to the longitudinal
axis of the lamp). The electrode 21, which is often referred to as
a heater or cathode is of a well known type used in rapid start
fluorescent lamps and includes a coating thereon which is usually
in the form of alkaline earth oxides applied thereto in the form of
carbonates which, upon processing, are converted to oxides.
The opposite end of the electrode 21 is connected to electrical
lead segment 11a which is, in turn, connected by way of an
electrode disconnect switch 23 and the electrical lead 11 to the
pin 17. The electrode disconnect switch 23 is preferably in the
form of a glass bottle 25 having a pair of electrical conductors 27
and 29 sealed into one end. A bimetal switch 31 is located within
the glass bottle 25 and connected intermediate the electrical
conductors 27 and 29. A meltable bypass member 33 is affixed to the
conductors 27 and 29 in shunting relationship to the bimetal switch
31, as shown in FIG. 1 only. Moreover, a vacuum or a gas fill of
noble gases or nitrogen or combination thereof is contained within
the glass bottle 25. Thus, electrical connection between the
electrode 21 and the pin 17 is effected by way of the electrical
lead segment 11a, the electrical conductors 29 and 27 of the
disconnect switch 23, with the bimetal switch 31 or the bypass
member 33 connected therebetween, as will be explained hereinafter,
and the electrical lead 11.
Alternatively, the electrode disconnect switch 23 may be in the
form of a bimetal switch 31 (i.e., without a bottle 25) having
either a substantially U-shaped or straight configuration which
would be located within the lamp envelope. Although a hermetically
sealed glass bottle 25 having a gas fill is preferable, the switch
31 may have an insulating cover or be disposed within a bottle
merely shielding the switch 31 from the electrode 21 or merely be
configured to protect the switch contact from undesirable
environmental factors. Also it is conceivable that the electrode
disconnect switch 23 could be of a form wherein the electrical
conductors 27 and 29 exit from opposite ends of the glass bottle
25.
Of course, there is an electrode 21 within each of the opposite
ends of the lamp envelope 5, FIGS. 1 and 2 showing just one end of
the lamp. The lamp can include only one disconnect switch 23 or
have a pair of switches 23, each connected to an electrode at each
end of the lamp.
As to manufacture, it is well known that the glass envelope 5 has
the glass stem member 9 inserted therein and sealed thereto.
Accordingly, it has been found most expedient to position the
electrode disconnect switch 23 in a manner such that the switch 23
is located between and does not extend beyond a pair of
substantially parallel planes extending in a direction normal to
the longitudinal axis of the electrode 21 and intercepting the ends
of the electrode 21. Thus, it has been found that the electrode
disconnect switch 23 is not normally disturbed when the envelope 5
is telescoped over the electrode 21 since the disconnect switch 23
does not extend beyond a plane normal to the ends of the electrode
21.
As to operation of the electrode disconnect switch 23, it is known
that the previously-mentioned alkali earth oxides on the electrode
21 are derived from a coating of carbonates during the
manufacturing process. Normally, this process is effected by
applying current to the electrical leads 11 and 13 in an amount
sufficient to raise the temperature of the electrode to about
1700.degree. C.
However, the bimetal switch 31, which is normally closed at room
temperatures, tends to operate or open at a temperature in the
range of about 140.degree. C. to 180.degree. C. in a 40-watt type
lamp. By 40-watt type is meant a T-12, 4-foot lamp operating at 350
to 475 ma, including both standard 40-watt lamps and lower wattage
energy saving lamps. Thus, the process temperatures employed to
bake and seal the envelope 5 to the glass stem member 9 would tend
to activate the bimetal switch 31. Moreover, current applied to the
leads 11 and 13 would fail to effect the desired 1700.degree. C.
temperature of the electrode 21 for processing the carbonates
thereon since the bimetal switch 31 is operational and would
interrupt the process.
In order to achieve this desired processing of the electrode 21
during manufacture, a bypass member 33 of a refractory material,
such as molybdenum or stainless steel, is connected across the
electrical conductors 27 and 29 of the electrical disconnect switch
23. This bypass member 33 is of a meltable material and in response
to an electrical pulse potential, such as a pulse from a 270
microfarad capacitor charged to 300 v D.C., is removed or melted
away after processing the carbonates to provide the desired
electrode disconnect switch 23 capability, this final condition
being shown in FIG. 2.
Additionally, it has been found that the position of the electrode
disconnect switch 23 with respect to the electrode 21 within the
lamp envelope 5 is important. Rapid start fluorescent lamps may be
of different wattages and of a length of 3, 4, 6 or 8-foot, for
example. It has been found that the electrode disconnect switch 23
should be spaced in the range of about 8.0 to 14.0 mm from the
electrode 21. More specifically, the positioning of the electrode
disconnect switch 23 should be such that the average spacing, X of
FIG. 2, between the switch 23 and the electrode 21 is not less than
about 8.0 mm and not more than about 14.0 mm. Also, the electrode
disconnect switch 23 should be of a material and configuration to
operate at temperatures in the range of about 75.degree. C. to
300.degree. C. depending upon the capacity of the lamp and the
location of the disconnect switch with respect to the electrode
21.
In the case of a 40-watt type T-12 lamp having a length of about 4
feet and operable at a current in the range of about 350 to 475 ma.
from a standard F-40 ballast, use of a pair of disconnect switches
23 in accordance with the invention resulted in an energy saving of
about 21/2 watts per lamp, while maintaining lumen output and lamp
life. The temperature necessary to operate the electrode disconnect
switch 23 in the above mentioned 40-watt type lamp is preferably in
the range of about 140.degree. C. to about 180.degree. C.
By way of example, it is to be noted that curve A of FIG. 3
provides a comparison chart for a 40-watt type rapid start
fluorescent lamp which compares relative lamp life, in percentages,
with the average distance of the disconnect switch 23 from the
electrode 21 at each end of the lamp. As can readily be seen, the
relative lamp life increases at a relatively rapid rate as the
spacing between the disconnect switch 23 and electrode 21
increases. However, this increased lamp life tends to level off at
a spacing of about 8.0 mm. Characteristics similar to those
illustrated by curve A of FIG. 3 are also applicable to lamps of
other wattages and sizes.
Tests indicate that a spacing between the switch 23 and electrode
21 of greater than about 14.0 mm. creates problems in achieving the
desired temperatures consistent with proper operation of the
disconnect switch 23.
Thus, there has been provided a rapid start fluorescent lamp which
includes an electrode disconnect switch having a capability for
effecting desired processing of an electrode as well as
disconnection thereof during operational use of the lamp. Also, the
electrode disconnect switch is positioned such that interference
thereof with the joining of an envelope and stem member is not a
problem and provision is made for removing the electrode heating
capability during manufacture.
While there has been shown and described what is at present
considered the preferred embodiments of the invention, it will be
obvious to those skilled in the art that various changes and
modifications may be made therein without departing from the
invention as defined by the appended claims.
* * * * *